Emerging adults, often referred to as people between the ages of 18 and 25 years,1,2 report a high prevalence of past-month cigarette smoking and heavy episodic alcohol use compared to other age groups in the U.S.3-6 Sexual minorities (SM; including lesbians, gays, and bisexuals, and those with same-sex behaviors attractions, or relationships) in emerging adulthood are more likely than their completely heterosexual peers to be current or daily smokers7-12 and to engage in heavy episodic drinking.12-15 These sexual-orientation disparities begin in adolescence7,13,16 and persist into later stages of the life course.17-20 Despite pronounced disparities in substance use for SM populations, there are few investigations about substance use trajectories in emerging adulthood for SM populations and how substance use during this transitional period impacts health and adjustment in later emerging adulthood. Furthermore, there is only limited understanding about the early risk factors of substance use for SM emerging adults. Accordingly, the proposed study will employ a developmental perspective45-47 to empirically test how early risk and protective factors across several domains predict tobacco and alcohol use trajectories in emerging adulthood for SM populations, and how these trajectories are, in turn, related to health consequences and adult adjustment outcomes in later emerging adulthood. Analyses will use data from SM participants collected principally during emerging adulthood in the Growing Up Today Study (GUTS), a large national cohort study begun in 1996. The Specific Aims are to do the following: 1) Estimate trajectory patterns of tobacco and alcohol use for SM populations during emerging adulthood; 2) Elucidate antecedents from childhood and adolescence that predict tobacco and alcohol use trajectory group membership; and 3) Measure the health consequences and adult adjustment outcomes of tobacco and alcohol use trajectory groups. The proposed Specific Aims are consistent with the goals of the National Institute on Drug Abuse (NIDA) and relate to NIDA's strategic plan to identify the characteristics and patterns of substance use and to understand how development influences the various risk and protective factors for substance use with the ultimate goal of preventing the initiation and escalation of substance use. To facilitate such research, the applicant will execute a training plan that builds and improves upon his knowledge and skills in longitudinal study design and data analysis, substance use and prevention research, human development theories and research, and SM health research. The applicant will conduct the proposed research with support from a dedicated and multidisciplinary mentorship team in a resource-rich environment at the University of Pittsburgh. Upon successful completion of this fellowship, the applicant will be well-poised to meet his long-term goals of attaining a faculty position and having an independent scientific research career in substance use and prevention with specialties in young SM populations.